Thermal unfolding of helices of a C-peptide analogue of ribonuclease A in sodium dodecyl sulfate solution.
The conformation of a 13-residue C-peptide analogue of ribonuclease A, suc-AET-AAAKFLRAHA-CONH2, in NaDodSO4 solutions with respect to temperature was studied with CD. The equilibrium constant of unfolding yielded a straight line in a van't Hoff plot. In 10 mM NaDodSO4, delta G mu = 120 cal/mol, delta H mu = 700 cal/mol, and delta S mu = 2.0 entropy units all on per helical residue. These values compared fairly well with the thermodynamic parameters of the uncharged helix-coil transition of (Glu)n in 0.1 M NaCl based on the theories of Zimm and Bragg and Zimm and Rice. The peptide was not unfolded at 75 degrees C completely. Even in water without surfactant it was not a "random coil."
Wu
C S
CS
Cardiovascular Research Institute, University of California, San Francisco 94143-0524.
Yang
J T
JT
D000595:Amino Acid Sequence; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D011487:Protein Conformation; D011489:Protein Denaturation; D012259:Ribonuclease, Pancreatic / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate; D012996:Solutions; D013696:Temperature; D001615:beta-Endorphin / Q000737:chemistry
D010446:Peptide Fragments; D012996:Solutions; D012967:Sodium Dodecyl Sulfate; D001615:beta-Endorphin; D012259:Ribonuclease, Pancreatic